No obvious relationship exists between the three kinds of AMPs and the resistance of Plutella xylostella larvae to Cry1Ac toxin.

The leaf-dip method was used to test the resistance of P. xylostella larvae (DBM-F) to Cry1Ac toxin. Fifteen third-instar larvae were tested for each of four toxin concentrations, and the bioassays were replicated four times. Experiments in which control mortality exceeded 10% were repeated. The LC50 values were calculated by Probit analysis. The AMPs or Cry1Ac toxin was fed to P. xylostella by the leaf-dip method: PxDef, PxMor and PxCec (5000 μg/mL) were fed to 3rd instar larvae separately, and their respective biological effects on P. xylostella, and the different proteins mentioned above (5000 μg/mL) were mixed with Cry1Ac toxin (5 μg/mL) and then fed to 3rd instar larvae to observe their respective effects on the virulence of Cry1Ac toxin. There were 3 replicates in each of the above treatments, with 15 third-instar larvae in each replicate. Biological data, including mortality (72 h), 4th instar, pupation rate, pupal weight, pupal length, pupal width, pupal stage, emergence rate, hatchability and adult longevity, were recorded for each treatment.